Thermoelectric refrigeration system



May 7, 1963 1-. M. ELFVING THERMOELECTRIC REFRIGERATION SYSTEM 4Sheets-Sheet 1 Filed Dec. 21, 1960 N \l N \k x I 3H8 J MN MW NM mm M W &0N 2 mm 5 3 G @N INVENTOR. THORE M. ELFVl/VG BY May 7, 1963 T. M.ELFVING THERMOELECTRIC REFRIGERATION SYSTEM 4 Sheets-Sheet 2 Filed Dec.21, 1960 INVENTOR. THOHE M. ELFVl/VG May 7, 1963 T. M. ELFVINGTHERMOELECTRIC REFRIGERATION SYSTEM 4 Sheets-Sheet 3 Filed Dec. 21, 1960mm lat. t. 2 c Q.

xrraex/nir T. M. ELFVING THERMOELECTRIC REFRIGERATION SYSTEM May 7, 19634 Sheets-Sheet 4 Filed Dec. 21, 1960 1, I, l I l INVENTOR. THOR-E M.ELFV/NG United States The present invention relates to a thermoelectricrefrigeration system and more particularly to a system suitable forcooling objects and liquids in direct contact with cooled surfaces. Theinvention is applicable for use in the medical and laboratory fieldwhere silent operation and convenient temperature control is desirable.

In my copending application Serial No. 47,161, filed August 3, 1960,there is described a thermoelectric refrigeration system which employsone or more hermetically sealed heat transfer systems in thermal contactwith thermoelectric modules. The present invention incorporates featuresof the invention disclosed in said copending application in arefrigeration system suitable for use in medical and laboratoryrefrigeration applications.

The refrigeration system according to the present invention ischaracterized by its flexibility and efiicient application on theobjects to be cooled. The system may include coolers which can be freelymaneuvered by hand as is preferable when used for medical cooling oforgans and parts of the body in connection with surgery. A medical orlaboratory refrigeration system, according to the invention, allowsexact, rapid and convenient temperature control of the contact surfacesused for the application of localized cooling and will permit acontinuous cooling at constant temperature for any length of time.

Surgery under refrigeration usually requires the cooling down of theorgan to be operated on to temperatures around -|-10+l5 C. Because ofthe large amount of blood circulating through organs like the brain orthe kidneys, the cooling down process can not be carried out locallyfrom the beginning. Thermoelectric cooling is by its nature limited torelatively small refrigeration capacities and does not at presentprovide suitable means for the rapid cooling down of the entire body.If, however, the body temperature first is brought down by conventionalmeans (ice bath, ice Water rubber blankets, etc.) to a temperature of,say +28 C., then the blood supply through the arteries to said organscan be partly or completed restricted so that local cooling down to thedesired temperature can rapidly take place. In this way the heart andthe main part of the body can stay .at a safe higher temperature whilethe organ operated on is locally cooled to a much lower temperature.

It is an object of the present invention to provide a thermoelectricrefrigeration system which can be used in conjunction with detachableprobes, cups, plates and other contact coolers of a great variety ofshapes. The detachable contact coolers may be continuously orintermittently cooled and placed in direct contact with body organs orparts, or for other localized cooling.

According to an other object of the invention, means are also providedfor cooling liquids or blood under complete temperature control.

It is a further object of the present invention to provide athermoelectric refrigeration system capable of providing a plurality ofcooling temperatures.

It is another object of the present invention to provide athermoelectric refrigeration system including a plurality of heat pumpswhich can be operated to provide a variety of temperatures andrefrigeration capacities.

Other objects and features of my invention will appear from thefollowing description of the invention with reference to theaccompanying drawings.

Referring to the drawings:

FIGURES la and lb are elevational views, partly in atent l 3,633,233Patented May 7, 1963 section, showing a thermoelectric refrigerationsystem incorporating the present invention;

FIGURES 2a, 2b, 2c and 2d show elevational views, partly in section, ofvarious contact coolers which may be employed in the present invention;

FIGURE 3 shows a thermoelectric blood or liquid cooler;

FIGURES 4a and 4b show in sectional, elevational views embodiments ofthe invention for obtaining relatively low temperatures; and

FIGURE 5 is a perspective view, partly in section, showing anotherembodiment of the invention in which a plurality of temperatures can beobtained from the same system simultaneously or independently.

In FIGURES la and lb, there is shown a thermocouple assembly or module11, which is in thermal but notelectrical contact with a hollowcondenser 12, preferably made from aluminum or copper. The condenser 12has a plane surface 13 thermally contacting the normally cold side ofthe modules 11 and is preferably provided with inside fins 14 extendingfrom the surface 13.

The normally warm side of the module 11 is in thermal contact with ahollow radiator 15. The radiator is provided with air-cooled outsidefins 16 for dissipating heat to the surrounds. Inside fins 17 extendfrom the surface which is in contact with the hot side of the module 11.The module 11 is supplied with unidirectional current, for example, adirect current, through the leads 18. The current is controlled byvariable resistor 19.

A reversing switch 20 connects the thermocouple module 11 and variableresistor 19 to a D.-C. power supply 21. Alternating current power issupplied to the power supply through a thermostat 23 connected to lead22. The thermostat has its temperature sensitive bulb 24 in contact withthe condenser 12 and can be set to interrupt or cut-off the A.-C. powerwhen the condenser reaches a predetermined temperature. The switch 20can be connected to reverse the current through the modules whereby thenormally cold side is heated, and vice versa, for purposes to bepresently described. It is apparent that other sources of D.-C. powermay be employed. Furthermore, other types of power control can beemployed in place of variable resistors. Various types of D.-C. suppliesare known in the prior art and will not be described here.

A thermometer 25 may be provided to indicate the temperature of thecondenser 12. The thermometer sensing element is disposed in thermalcontact with the condenser.

The condenser 12 normally forms the upper heat dissipating part of aclosed heat transfer system partly filled with a suitable volatileliquid such as Freon 114 or similar nonpoisonous refrigerant. The restof this heat transfer system comprises a pressure resistant insulatedhose 26 connected to the bottom part of the condenser, a coupling 27 anda hollow metal body 28, which in FIGURE la is shown in the form of apipe or cylinder. The lower portion of the heat transfer system is shownattached to a holder 29, in which position the heat transfer system justdescribed is inactive with the filling stored in the insulated hose.

The hollow radiator 15 is partly filled with a similar heat transfermedium in liquid contact with the inside fins 17, which part of theradiator serves as a heat absorbing boiler while the upper and outsideportion serves as a heat dissipating condenser cooled by air throughnatural convection or by help of the fan 30.

The described part of the invention functions in the following way:After closing the switch 20 in a refrigeration position, D.-C. currentis supplied to the thermoelectric module 11 whereby the condenser '12 iscooled and the radiator 15 is heated by the heat pumping action of thethermocouple. As soon as the cylinder 28 is taken constitutes the lowestpart of the described heat transfer system, the volatile liquid willfill the hollow body 28 and start boiling until the temperature of thebody 28, which according to the invention, constitutes a contact coolerhas reached the approximate temperature of the condenser-12, The heatgiven ofl in the condenser 12 will be absorbed by the cold junctions ofthe thermocouple assemblies 11. The heat pump delivers heat energy at ahigher temperature to the radiator 15 where it is absorbed in the boilerportion and finally dissipated to the air through the fins 16. Thetemperature of the condenser 12 and thereby also of the hollow pipe 28can be regulated by the variable resistance 19 but can never go lowerthan the setting of the thermostat 23 as previously indicated.

As indicated in FIGURE 1b, the condenser 12 can be divided into severalseparate condensers, each provided with its own closed heat transfersystem as previously described, but all together using the radiator 15as the final heat dissipating device. the drawing lb is shown how eachof these separate condensers is provided with thermoelectric modules inseries whereby the current can be controlled by the same rheostatmodula- 'tor and the same thermostat. It is, however, obvious that theindividual condensers, according to the invention, can be cooled by heatpumps which are individually fed with D.-C. current from the powersupply through separate rheostats so that an individual temperaturecontrol for each heat transfer system can be obtained. Each heat pumpsystem can also be provided with its own thermostat for the control ofthe desired temperature limit. Each heat pump system can also beprovided with its own D.-C. power supply, in which case the thermostatsare acting on the A.-C. supply lines leading to each individual powersupply. Each condenser system may be, as indicated in FIGURE 16,provided with its own thermometer.

As a safety measure, the radiator 15 can also be divided into as manyhermetically closed heat transfer systems as there are condensers, eachradiator mounted beside each other as indicated on the drawing. Eachheat pump system will then be independent of the other with exception ofthe insulation and the support. It goes without saying that byseparately insulating each heat pump system and arranging electricconduits in a suitable manner, the heat pumps included in the panel canbe made completely inde-.

pendent and their temperatures adjustable in'relation to each other.

The shape of the. hollow contact coolers 28 which, according to theinvention, act like a boiler in a closed heat transfer system will bediscussed later. v denser can be connected with more than one contactcooler by having more than one hose connected to its condensing area orby forking the hose into two or more hoses each provided with itscontact cooler of suitable shape. such a multiple array of contactcoolers working on a common condenser has to be larger than the volumeof one or more of the contact eooler boilers with their connectinghosesin order to avoid the possibility that some of the coolers run dry'byaccumulation of the liquid heat transfer medium in other cooolers.

In FIGURES la andlb, the panel of thermoelectric contact cooling heatpumps is shown mounted on a shelf 31 supported by a stand 32, on whichanother shelf 33 is arranged for the power supply, thermostat, control Irheostat and other electric equipment. The height of the shelf 31 isadjustable in any known way so that the flexible hoses can be extendedif necessary for the unhampered flow of heat transfer'medium between thecontact coolers and the condensers.

The rectifier or power supply shown in the drawings One con- Theamountof liquid heat transfer medium in 'by using self-closingdisconnect couplings as indicated by 27 in FIGURE la. Such couplings canbe used for refrigeration lines under pressure and can also be used hereunder certain conditions, in which case the hollow heat absorbing partor boiler of the heat transfer system on the cold side of the modulescan be given any suitable form for contact cooling. It can, forinstance, be shaped like a double walled bowl as later illustrated inFIGURE 2a. In connection withsurgery, the sterilization requirements areso strict that steaming at temperatures 'of +300 F. and above aredesirable. Under such circumstances, detachable secondary contactcoolers are preferable.

Such contact coolers according to the invention comprise a primaryhollow cooler in the form of a cylinder or probe serving as boiler inthe thermoelectn'cally cooled heat transfer system and a secondarydetachable solid cooling body in intimate thermal contact with theprimary cooler and shaped according to the organ to be cooled.

FIGURE 2a shows a contact cooler for brain surgery. The primary cooler41 comprises a hollow cylinder attached to the flexible hose 42 andprovided with extended surfaces on the inside as illustrated by thecross section detail shown in FIGUREZIJ. The secondary cooler comprisesa hollow metal shaft '43 in which the primary cooler is inserted with aclose fit. The shaft 43 forms a continuation of a bowl-shaped contactsurface 44 of a size and shape corresponding to the brain of the patientunder surgery. The upper part of the bowl 44 and the shaft 43 is coveredby a plastic compound 45 which is extended into a handle 46 around theprimary cooler to prevent condensation on top of the secondary contactcooler. The plastic compound used will resist sterilizationtemperatures. In order to avoid significant temperature differences inthe secondary detachable cooler, more than one primary cooler can beused as illustrated by FIGURE 20, whichshows two primary metal boilersinserted into two shafts of the secondary cooler.

FIGURE 2d illustrates a double secondary cooler for the use inconnection with kidney surgery. The flexible ho se 51 is forked into twohoses 52 and 53 leading to the primary cooling tubes 54 and 55 to whichthe kidneyshaped contact coolers 56 and 57 are attached. The

contact coolers can suitably be made from aluminum,

stainless steel or chrome plated copper. The movable contact coolers canenclose a kidney from two sides and cool it down to a predeterminedtemperature in short time, whereafter one or both of the coolers can beremoved.

In FIGURE 3 is shown how the invention is used for the cooling of bloodor other-liquids in relatively small quantit es. In FIGURE 3 is shown aflexible-hose 61 which in itsupper end is attached to'ather-moelectrically cooled condenser as previously described. The hose61 is connected to a hollow metal tube 62 which constitutes the pr marycooler as described in FIGURE 2a. Around the primary cooler 62 is placeda glass tube 63 with inlet and outlet connections 64 and 65. The glasstube is sealed to the metal tube 62 by rubber stoppers 66 and 67. Bycirculating blood or other liquids through the glass container, it willbe cooled by the central cooler 62 in a self-explanatory way.

When applying cooling to human tissues or organs in connection withsurgery, the desirable temperature of the contact cooler usually is notlower than 0 C. or

slightly below. In certain cases, such as cautery and for externaltreatment, much lower temperatures can be used and a medicalrefrigeration system according to the invention can, for such purposes,provide low temperatures by means of another embodiment of theinvention. FIGURES 4a and 4b show details of special embodiments of theinvention whereby very low controllable temperatures can be obtained forultra-cold cautery and other purposes.

In FIGURE 4a, 71 represents a thermocouple assembly supplied with D.-C.current through the cable 72. The cold junctions are glued toapreferably grooved aluminum plate 73, which is in close thermal contactwith a condenser 74. The condenser 74 together with a flexible hose 75and a metal hollow probe 76 attached to this hose form a hermeticallyclosed heat transfer system functioning as previously described. Theprobe 76 as well as the condenser 74 are preferably provided with insideextended surfaces. The hot junctions of the assembly 71 are in a similarway glued to a preferably grooved highly conductive plate 77, which isin close thermal contact with the metal wall 78 which is preferablyprovided with fins 79. The wall 78 is part of a vessel or container 80which, according to the invention, is filled with crushed ice and servesas a heat sink of about 0' C. temperature for the describedthermoelectric heat pump. The ice container 80 has a lid 81 and ispreferably insulated by the insulation 82. The condenser 74 is similarlyheavily insulated with insulation 83 and so is the flexible hose 75 bythe flexible insulation 84. The probe 76 may be provided with aninsulated handle 85.

Because of the low temperature heat sink at the hot junctions, aone-stage thermoelectric heat pump can easily bring the temperatures onthe cold junctions down to 40 C. or below, which temperatureconsequently will be attainable on the contact probe 76.

By controlling the current supply to the thermocouple assembly by meansof a rheostat, a complete control of the temperatures can be achieved.

In FIGURE 4b is shown a similar arrangement for a two-stagethermoelectric heat pump assembly whereby the temperature can be broughtdown to -90 C. or below. The first stage thermocouple assembly 86 is onits cold junction side glued to a metal plate 87 of approximately thesame thickness as the thermoelectric assembly itself and preferablygrooved on both sides. The plate 87 is in thermal contact with thecondenser 88 which, together with the insulated hose 89 and the hollowprobe 90, constitute a hermetic heat transfer system which is filledwith suitable volatile liquid whereby the probe 90 is cooled toapproximately the same temperature as the cold junctions of the firststage assembly 86 previously described. The hot junctions of theassembly 86 are glued to a similar metal plate 91 which is in thermalcontact with an intermediate plate 92 of highly conductive materialwhich on the other side is in thermal contact with the cold junctionside of the second stage thermocouple assemblies 93 over preferablygrooved metal plates 94 glued to the hot junctions of the assemblies 93.The hot junctions of the Second stage assemblies 93 are, through similarmetal plates 95, in thermal contact with a plane wall 96 provided withfins 97 and forming a part of a container 98. The insulated container isfilled with ice and serves as a heat sink for the dissipation of thetotal heat given off by the two-stage heat pump system. By maintainingan overall temperature difference in each stage of 45 C., afinaltemperature of 90 C. is possible on the probe for cautery and otherultra cold applications. The condenser 88 as well as the hose 89 isprovided with a heavy insulation. The handle 99 on the probe canpreferably be heated on the outside surface by an electric wire asillustrated in the drawing. The two thermocouple assemblies have theirheat pumping capacity balanced to each other and can be supplied withD.-C. current in series with each other through the cable 100. Theultimate temperature of the probe can, as previously 5 described, beregulated by a variable resistance illustrated in FIGURE 1.

FIGURE 5 shows an embodiment of the invention whereby both medium lowand very low temperatures can be produced by the same thermoelectricheat pump equipment for application in contact coolers or for otherpurposes. The numeral 101 represents one of several thermocoupleassemblies in thermal contact on their hot junction side with the castaluminum radiator 102 provided with fins 103 and cooled by the airstream from the fan 104. The thermocouple assemblies represented by 101,which on both sides are glued to grooved relatively thin aluminum plates105, are on their cold sides in thermal contact with the hollowcondenser 106 of a hermetic heat transfer system filled with a volatileliquid as previously described. Other parts of this hermetic system arethe flexible hose 107 and the metal plate evaporator 108 for contactcooling of large surfaces in accordance with the invention as previouslydescribed. On the other side of the condenser 106 and in close thermalcontact therewith is shown a single thermocouple assembly 109 which alsois connected on both sides to heat equalizing plates 110 similar to 105.The thermocouple assembly 109 has its hot junction side facing thecondenser 106 and its cold junction side in thermal contact with acondenser 111 which forms the heat dissipating part of a second hermeticheat transfer system comprising the insulated hose 112. and the hollowprobe 113 and functioning as previously described.

Shown in the figure are electric leads for supplying D.-C. current tothe thermocouple assemblies and electric switch means for disconnectingthe current to the single assembly 109 when temperatures below freezingare not wanted.

The condenser system 111 with its thermocouple assembly 109 forms afirst stage low temperature heat pump system cooled by the condenser 106and its thermo couple assemblies 101, which constitute a second stageheat pump system in relation to the described first stage, but whichalso independently through its hermetic heat transfer system can delivermedium temperature cooling to surrounding objects. Both stages candeliver their cooling effect simultaneously when both the hose 1'07 andthe hose 112 are in an active lower position. When the hose 107 is in araised position as illustrated in the figure, the external load oncondenser 106 will discontinue and only the first stage low temperaturesystem is active. In the same way, the hose 112 with its probe 113 canbe raised in an inactive position in which the first stage heat pumpsystem is picking up no external heat load. When no low temperatures arewanted, the current supply to the first stage assembly 109 canpreferably be cut off with maximum capacity on the medium temperaturesystem as a result.

It is also possible to reverse the current in the thermocouple assembly109 by a suitable switch so that its cold side will be facing thecondenser 106, while its hot junction side faces the condenser 111 whichnow becomes a boiler. The hose 112 with its probe 113 can preferably bein a raised position so that the volatile liquid fills the hollow vessel111, where it will boil under heat absorption. The probe 113 will nowserve as an air cooled condenser and can be provided with detachableextended surfaces of known type. The heat pumping capacity of thethermocouple assembly 109 will now be added to the refrigeration effectof the assembly 101 on the other side of the condenser 106. In order toincrease the heat pumping capacit of the assembly 109 in this reversedcurrent position, the hermetic heat transfer system belonging to thecondenser 111 can be extended by a pipe 114 to an extra heat dissipatingmember 115 located above the member and preferably air cooled asindicated by dotted lines in FIGURE 5. Such a heat dissipating memberwould have no influence on the functioning of assembly 109 as a firststage low temperature system but would increase its capacity whenworking, as described, together with the assembly 101. Thus, all thethermocouples included in the heat pump equipment can work together asan eificient single-stage system when no low temperatures are wanted ormaximum capacity of the medium temperature system is needed.

Experiments have shown that a combined one-stage and two-stage system,as described, with a hollow member serving both as a condenser on thecold junction side of a medium temperature heat pump system and as aheat sinkon the hot junction side of a low temperature heat pump systemis the most efficient way of obtaining two diflereht temperature rangesfrom the same equipment.

' The two stages have to be balanced to each other as described in mycopending application Serial No. 47,161, 'thatis, the heat pumpingcapacity of the second stage has 'to correspond to the number of B.t.u.sabsorbed by the heat absorbing parts of both hermetic systems plus theenergy supplied to the first stage thermocouple assembly. The energyinput to the first stage which for many applications below freezing canwork with a relatively small AT between the hot and the cold junctionsis normally only /6 /3 of the energy input to the second stage, and "thecurrent through the first stage module can often be only half or less ofthe current fed to the second stage modules. Means may be provided forseparately regulating the current to the two stages. By arrangingthreeor, more stages in the same way, it is possible to simultaneouslyprovide three or more temperature ranges from a thermoelectric heat pumpassembly, if desirable.

The primary metal coolers can, according to the invention,-besterilized-simply by raising the flexible part of the heat transfersystem to a position indicated by dotted 'lines in'FIGURE lb andreversing the current through Jthe thermocouples so that the module willheat the con- "denser 12 instead of cooling it. In this position, the

volatile liquid in the secondary system will flood the condenser whichnow becomes a boiler under increased pressure. the temperature of thewhole heat transfer system so The volatile liquid and vapor willequalize that the metal body 28 assumes the same high temperaible heattransfer system connected to the normally cold [side of thethermoelectric heat pump equipment can be located'in three positions:One position in which the heat transfer system is inactive; a secondposition in which the'contact-coolers are applied; and a third positionm "which the contact coolers are being heated.

It is apparent that the refrigeration system described can be used inmany applications other than in the medi- "cal and laboratory field.Reference to these fields was for purposes of illustration, and theinvention is not mtended to be limited in this respect.

I claim: l. A thermoelectric heat pump comprising athermoc'onple'assembly having hot and cold junctions, a condenser inheat exchange relationship with the cold junctions of said thermocoupleassembly, an evaporator, a

" flexible hose forming a hermetic connection between said 'evaporatorand condenser to thereby form a hermetically sealed system and avolatile liquid partly filling said hermetically sealed system, saidflexible hose Permitting positioning of the evaporator whereby the samemay be operative or inoperative.

2. A-thermoelectric heat pump comprising a thermocouple assemblyhaving'hot and cold junctions, a condenser in heat exchange relationshipwith the cold junctions or said thermocouple assembly, an evaporator, a

flexible hose forming a hermetic connection between said evaporator andcondenser to thereby form a hermetically sealed system, said flexiblehose permitting positioning of the evaporator whereby the same may beoperative or inoperative, a volatile liquid partly filling saidhermetically sealed system, means for applying an electric current tosaid thermocouple assembly, means for regulating said current andcontrol means for sensing the temperature of the condenser andcontrolling application of current to the thermocouple assembly.

3. A thermoelectric heat pump comprising a thermocouple assembly havinghot and cold junctions, a condenser in heatexchange relationship withthe cold junctions of said thermocouple assembly, a metal evaporator, aflexible hose forming a hermetic connection between the evaporator andthe condenser to thereby form a hermetically sealed system, a volatileliquid partly filling said hermetically sealed system, said flexiblehose permitting positioning of the evaporator whereby the same may beoperative or inoperative, and-a'metal contact cooler detachablyconnected to said metal evaporator.

4. A thermoelectric heat pump as in claim 3 wherein said detachablemetal contact cooler is shaped to accommodate a kidney.

5. A thermoelectric heat pump as in claim 3 wherein said detachablemetal contact cooleris shaped to accom- -modate a brain.

6. Arthermoelectric heat pump system comprising a thermocouple assemblyhaving hot and cold junctions, an air cooled hermetically sealed heattransfer system having heat absorbing and heat dissipating parts in heatexchange relationship with the hot junctions of said assembly to coolthe same, a second hermetically-sealed heat transfer system having heatabsorbing and heat dissipating parts having its heat dissipating part inheat exchange relationship with the cold junctions of said thermocouple,said second heat :transfer system having a flexibleconnection betweenthe heat absorbing and heat dlssipatmg parts thereof, said flexible hosepermitting positioning .of the evaporator whereby the same may be"assembly, a second thermocouple assembly havinghot and cold junctions,a second condenser forming the heat dissipating parts of a secondhermetic heat transfer system, said second condenser in heat exchangerelationship with both the hot junctions of the first thermocoupleassembly and the cold junctions of said second thermocouple assembly'andcooling means in heat exchange relationship with the hot junctions ofsaidsecond thermocouple assembly.

9. Apparatus as in claim 8 in whichsaid means for cooling the hotjunctions :of said second thermocouple assembly comprises an air-cooledradiator.

10. A thermoelectric heat pump as in claim 8 wherein an evaporator isconnected to one of said first and second condensers by a flexiblecoupling whereby said evaporator may be disposed to be operative orinoperative.

11. A thermoelectric. heat pump system as in claim,8 wherein evaporatorsareconnected to the condensers of the first and second hermetic transfersystems by a flexible coupling whereby said evaporators may be disposedto be operative or inoperative.

12. A thermoelectric heat pump comprising a thermocouple assembly havinghot and cold junctions, a condenser in heat exchange relationship withthe cold junctions of said thermocouple assembly, an evaporator, aflexible coupling forming a hermetic connection between said evaporatorand condenser to thereby form a hermetically sealed system, saidflexible hose permitting positioning of the evaporator whereby the samemay be operative or inoperative, a volatile liquid partly filling saidhermetically sealed system, means for applying a unidirectional electriccurrent to said thermocouple assembly, and reversible switching meansfor controlling the polarity of said current.

13. A thermoelectric heat pump comprising a thermocouple assembly havinghot and cold junctions, a condenser in heat exchange relationship withthe cold junctions of said thermocouple assembly, an evaporator, aflexible hose forming a hermetic connection between the evaporator andthe condenser to thereby form a hermetically sealed system, saidfleinble hose permitting positioning of the evaporator whereby the samemay be operative or inoperative, a volatile liquid partly filling saidhermetically sealed system, and means encircling said evaporator todirect a liquid to be cooled over said evaporator.

14. A thermoelectric heat pump system comprising a thermocouple assemblyhaving hot and cold junctions, a hermetically sealed heat transfersystem having heat absorbing and heat dissipating parts with the heatdissipating parts in heat relationship with the cold junctions of saidthermocouple assembly, a liquid bath in heat exchange relationship withthe hot junctions of said thermocouple assembly, said heat transfersystem having a flexible connection between the heat absorbing and theheat dissipating parts thereof.

15. A thermoelectric heat pump system comprising a first thermocoupleassembly having hot and cold junctions, a condenser forming the heatdissipating part of a hermetic heat transfer system in heat exchangerelationship with the cold junctions of said first thermocoupleassembly, a second thermocouple assembly having hot and cold junctions,the cold junctions of said second thermocouple assembly in heat exchangerelationship with the hot junctions of said first thermocouple assemblyand a liquid bath in heat exchange relationship with the hot junctionsof said second thermocouple assembly, said heat dissipating part of saidhermetic heat transfer system having a flexible connection with the restof the system.

References Cited in the file of this patent UNITED STATES PATENTS1,804,072 Turrettini May 5, 1931 1,859,953 Boyer May 24, 1932 2,111,904Schlumbohm Mar. 22, 1938 2,188,574 Love Jan. 30, 1940 2,415,455 BarnesFeb. 11, 1947 2,922,284 Danielson Jan. 26, 1960 2,932,953 Becket Apr.19, 1960 2,947,150 Roeder Aug. 2, 1960 2,966,033 Hughel Dec. 27, 19602,978,875 Lackey Apr. 11, 1961

1. A THERMOELECTRIC HEAT PUMP COMPRISING A THERMOCOUPLE ASSEMBLY HAVINGHOT AND COLD JUNCTIONS, A CONDENSER IN HEAT EXCHANGE RELATIONSHIP WITHTHE COLD JUNCTIONS OF SAID THERMOCOUPLE ASSEMBLY, AN EVAPORATOR, AFLEXIBLE HOSE FORMING A HERMETIC CONNECTION BETWEEN SAID EVAPORATOR ANDCONDENSER TO THEREBY FORM A HERMETICALLY SEALED SYSTEM AND A VOLATILELIQUID PARTLY FILLING SAID HERMETICALLY SEALED SYSTEM, SAID FLEXIBLEHOSE PERMITTING